Method of purifying tetraphosphoric acid



mme cg, ze .ieee

ci iegeeiice No gigniiceiiom il, iw?,

emi Arseneev in their @ministry (i923) was HPcOxs, ciad. i cciievc is correct for tetropicsgihoiic ecici in e pure form es produced by the iniecmiory methods use cy them and icy Fieinn nnciH-enncberg in m43.

` Commerciali teirophospooric acid has been re" centiy mocic avaiieicic @mi has been supposeto 'nave the alcove formule.. Ii, is o thick syrup, and, unizii the research on which my provino?) patents were boceci, had no apparent utility, it boing merely incidental or e bmpoduci, io "me menu.- feciure of certain forms ci phosphorous. The present commercial tcizrophospiioric acid appears to have been produced after time directions given by Bahama and irscneev by diseoiving P205 in wia-ter end probably Wihcii; the ageing feetme o1? their prcceaoa My prmni invention relates to o. proceso of manufacturing pure tetrepi'iospsioric acid, or the process or ri/ep of puricaition o' such coerciel tetraphosxchoric acid. Ass lecci' show, my pure tetrephcspnoric ecid is a complete ncveity, at leest when viewed as e eommeroiei product,

and I so ciaim it.

.For m @ses in which I ccnempicte the uae o2 ci 100% pure tetraphosphorio acid, or one so neerly so os to be resuitentiy equivalent, the matter of purity on o, practical or commercial basis wos perouni.

In my research locking to the production of Suche. pure or substantially pure tetrepixosphoric (ci, ccf-fiom pyropilosphoric acid content without substantiel icss so that by e, simple processing I could attain tetrcpimsphcric cciii of c; purity of 169% or practically so, M

21s is Weilknovm, phosphorus is formica lin the mma-zoe from iriceicium nhospiiatc QcnPOca icy reductionwith corbon end siiico..- The reaction eccgcieoo2+icc+ceio2=coecios+fip+icco amgoi-i-Pgomemo orina-pcmchmc ccici Sometimes the F205 tends not to combine with the weber but "cubicles up through. it as c, smoke end io get iis storied mechanically it is dcsirobie 25 to cdd phccphoric ecici to the water ot the stort. Toe rient resection wouici be @'f' O4+PeOs=3HcPa0v (pyro-phosphoric acid) 31H4P21+Pz0a=2HcPiOm (tetra phosphoric acid) This lost reaction does not run to 'a complete emi end when' sumcieni; P205 to form HcPOn has been added there is stili come HePzO': left in the .syl-up, for the materiel is in theform of c syrup. l If continued to edd more P205 I will have more than. the required annuncia-izo form the Hamon.

Therefore, I stop the reaction at this point when the 'equilibrium 'is reached which contains ep- Iproixilrrieitelf?. 17%%'of HiPaOq, and 825420Z, of 45 jiiHsHiOis. mis vis epproetely the composicion of the commercial scr-coiled "pure teimpnosphoric acid.

ii; is evident tthe reaction for 'the preparacon of cetraphoric acicby passing P205 mw 50 ifi if the proportion of water is not correct, the iollowing reaction will have taken place PaQs-i-2HzO=H4P201 It will be seen, therefore. that in the passing of e. the P205 into the water, an equilibrium is evidently formed when the P205 reacts with the water and we have this mixture of pyrophosphoric acid and tetraphosphoric acid. Following this theory I tried experiments in which I kept the water in excess and ran similar tests, keeping the P205 in excess duringthe process of the reaction, but found in each case on test for impurity my lresultant acid contained pyrophosphoric acid in large amount.

. I havealreadydescribed is the removal of water lI then reached my 'concept of a procedure to convert the mixture into pure tetraphosphoric acid, and I have discovered that by heating to 450-550 C. or 842-932 F., I amable to convert` my mixture of pyrophosphoric acid and tetraphosphoric acid into a. material of 100% tetrafs phosphoric acid.

The amount of time depends on the amount oi material and the shape of the vessel containing it. A large amount would require several hours in a furnace, and under any circumstances it should be spread out in a fairly broad shallow layer. In a small amount of 20 or 3G grams, it has been my habit to use a small porcelain dish and the reaction takes In this I drive of one molecule ci water from the pyrophosphoric acid impurity, converting the material entirely into tetraphosphoric acid.

Whatever remainder there is of the pyro ory other non-tetraphosphoric content is sc .nearly merged that in any subsequent reaction, as in forming an acid sait, the equation seems to clear vitself and leave the absolutely pure tetraphosphorlc acid, as' far as we yet know it.

The reaction for the purification of the tetraphosphoric. acid from its impurity by heating as from the pyrophosphoric acid impurity, this causthe material is heated two molecules of the water is as follows: 2PaOs+3H2O=HP4O1a but ing it tov form tetraphphorlc tion as noted is 2H4P2o1+ (neat) :melon-mo the graphic formula for which is:

acid. The reacv I have a good experimental basis for 'these formulas because-I have proven that the tetraphosphate radical goes easily to the pyro, but not so easily to the ortho, and not at all to the meta, by hydrolysis. Boiling with either strong acid or alkali will cause it to decompose into the pyro and then ortho, but the pyro is :formed iirst and the ortho by further chemical action.

By controlling the teinperattire7 the rate ci reaction' in the pyrophosphoric impurity may be' so gauged that a tetraphosphorie acid is pro-1 duced which is liiii% pure cr practically so.y It is obtainable as a syrup which is 100% HhOn which is the pure tetraphosphoric acid itself and does not need any crystallizing out as Rakuzin and irserieev suggesd.

What I thereioreclaim and desire to secure by LettersV Patent isf l. The process of purifying tetraphosphoric acid containing pyrophosphoric acid as an impurity, which comprises heating.r the impure tetraphosphoric acid to a temperature approximately between 450 C. and 550 C. for a suicien-fJ length of time to eliminate water in the ,proportion of one molecule ci water from every two molecules of the pyrophosphoric acid and thereby to convert the sameintc tetraphosphoric acid. y 2. In the process ci purifying tetragiiosphcric acid containing pyrophosphoric acid as an impurity, that step which consists in changing the pyrophosphoric acid to tetraphosphoric acid by heating the same to a temperature and for a suf- :cient length of time to eliminate water in the proportion ci one molecule of water from every pyrophosphoric acid.

AUGUSTUS H. FISKE. 

